Insect cell-based impedance biosensors: a novel technique to monitor the toxicity of environmental pollutants

Cell biosensors are currently emerging as novel, sensitive techniques to monitor the toxicity of environmental pollutants. Here, we have developed electric cell-substrate impedance sensing (ECIS) for on-line monitoring of the behavior of insect cells. Cells were cultured on a microarray of eight small gold electrodes, deposited on the bottom of tissue culture wells. Upon inoculation, cells showed a tendency to drift downward and attached to the gold surface precoated with the protein Concanavalin A to accelerate the cell attachment. The impedance increased because the cells acted as insulating particles to restrict the current flow. The resulting impedance, a coordination of many biological reactions within the cell, was continuously monitored in real-time to reveal information about cell spreading and micromotion. As the cell behavior was sensitive to external chemicals, the applicability of ECIS for inhibition assays was demonstrated with HgCl₂, 2,4,6-trinitrotoluene (TNT), 2-amino 4,6-dinitrotoluene (2-ADNT) and 1,3,5-trinitrobenzene (TNB). Electronic Publication     

Chemical defense: incorporation of diet-derived pyrrolizidine alkaloid into the integumental scales of a moth (<Emphasis Type="Italic">Utetheisa ornatrix</Emphasis>)

Summary. Evidence is presented that pyrrolizidine alkaloid acquired by Utetheisa ornatrix (Lepidoptera, Arctiidae) as a larva from Crotalaria foodplants is incorporated in part into the scales of the adult. A single forewing of a male or female moth may contain in the order of 6 to 13 g monocrotaline in its scale cover or about 1 to 2% of the moths systemic monocrotaline content. Based on estimates of the number of scales per forewing, the monocrotaline content of individual scales is calculated to be in the order of 0.1 and 0.2 ng monocrotaline per male and female scale, respectively. This amounts to concentrations of about 1 and 3%, values roughly at a par with the average systemic concentration (0.5-0.6%) previously determined for monocrotaline in Utetheisa. It is argued that the presence of pyrrolizidine alkaloid in the moths scale coating could account for the promptness with which adult Utetheisa are rejected by spiders. It is suggested further that chemical impregnation of scales with substances deterrent to predators may be more widespread among insects than generally assumed.     

A reliable indicator of female fecundity: the case of the yellow belly in<Emphasis Type="Italic"> Knipowitschia panizzae</Emphasis> (Teleostei: Gobiidae)

A large body of research has developed on male ornaments and their role in sexual selection while female ornaments have been less investigated. This study focused on the presence, function, and possible role of a sexually dimorphic nuptial trait as an indicator of female quality in a fish species presenting conventional sex roles: the yellow patch on the belly of Knipowitschia panizzae females. Aquarium spawning experiments demonstrated that this ornament is due to dermal pigments, is displayed only when the female is ready to spawn, and is switched off within minutes from the end of egg deposition. This sexual trait is variable in size among females and indicates female fecundity relative to her own body size. As a consequence, female yellow belly appears to be a reliable indicator of female quality as measured by current fecundity. Field data on natural nests highlights that males usually perform parental care on only one egg batch at a time. The modality of egg deposition suggests that males may be limited in their potential reproductive rates by environmental factors. Male limitations in egg care could favour male choosiness and the evolution of female nuptial displays.Communicated by R. Cattaneo-Vietti, Genova     

Reproduction and colony integration of the sea pen<Emphasis Type="Italic"> Virgularia juncea</Emphasis>

The distribution of fertile polyps, and the functional variations of polyps within sea-pen colonies, were investigated in Virgularia juncea, a species inhabiting shallow waters in the Penghu Islands, west of Taiwan. This gonochoristic species started gametogenesis between July and September, and mature gametes were broadcast in late summer the following year. Fertile pinnae and their constituent polyps were located in the middle region of the rachis; the upper and lower regions were infertile. Within the fertile regions, fecundity per centimeter decreased linearly toward the tips of the colonies. Abundant zooxanthellae were found in the upper part of the rachis; algal densities decreased down the axis of the colonies, and no algae were present in the lower part. New pinnae were generated only at the basal part of the rachis, They moved upward in relative position with growth of the colonies. These young pinnae near the peduncle were small and infertile. With time, they became fertile and started to harbor a few zooxanthellae. The old pinnae at the upper part of the rachis were large and infertile and contained numerous zooxanthellae. The tips of the colonies were often damaged, and the bare axial rods there were often fragile and could be easily broken off. The developmental gradient of pinnae (and their constituent polyps) along the axes of the colonies, coupled with the environmental gradient within a sea-pen colony, facilitates the functional differentiation within the rachis that may be an adaptation for inhabiting the interface between the water column and the sediment.Communicated by P.W. Sammarco, Chauvin     

Effects of dietary fatty acids on the reproductive success of the calanoid copepod<Emphasis Type="Italic"> Temora longicornis</Emphasis>

Egg production and hatching success of the copepod Temora longicornis were measured in laboratory experiments and in the field (North Sea). In the laboratory, ingestion of four algal species (Thalassiosira weissflogii, Phaeocystis globosa, Isochrysis sp. and Dunaliella tertiolecta) was followed and the content of fatty acids in the algae was determined. The two food types (T. weissflogii and Isochrysis sp.) that provided the highest ingestion of carbon and long chain fatty acids also resulted in the highest egg production rate (E_r) and hatching success (H%). In contrast, D. tertiolecta led to both low ingestion of carbon and long chain fatty acids, resulting in low reproductive success. There was a positive relationship between the amount of eicosapentaenoic fatty acid [20:5(n-3), EPA] ingested and E_r and H%, and of the ratio between docosahexaenoic and eicosapentaenoic fatty acid [22:6(n-3)/20:5(n-3), DHA/EPA] in the ingested food and H%. In the field, chlorophyll a and specific fatty acids were measured and protists were enumerated, in order to investigate the link between these factors and the reproductive success of T. longicornis. Hatching time was found to be related to temperature and exceeded 120 h at 6°C. No relationship was found between chlorophyll a and reproductive success (E_r or H%). E_r correlated with the concentration of diatoms and ciliates, which were the dominating protists in early spring, indicating that food quantity was the limiting factor for E_r. As in the laboratory experiments, H% was dependent on the fatty acid DHA and the ratio of DHA/EPA, which indicates that the quality of eggs (H%) is linked to the quality of food.Communicated by M. Kühl, Helsingør     

Variation at local scales need not impede tests for broader scale patterns

Ecologists are not always mindful of the constraints imposed by their scale of observation and sometimes prematurely attempt broad generalisations or become mesmerised by local details depending on their predilections. We specifically chose a character that is known for its local and unpredictable variation (morphology of kelp) to test the effect of scale on our ability to determine spatial patterns. We compared the morphology of Ecklonia radiata between monospecific and mixed stands of canopy-forming algae across temperate Australia (>5,100 km coastal distance) within a hierarchy of several spatial scales. While E. radiata specimens were generally larger in monospecific than in mixed stands, we failed to observe differences in morphology between stands at many sites and locations. Despite substantial local variation, differences between stands became increasingly clear at broader scales. The frequency of inconsistent differences between stands was greatest at local scales (sites separated by kms), intermediate at intermediate scales (locations separated by 100s of kms) and least at regional scales (regions separated by 1,000s of kms). These observations support the idea that large scale patterns can emerge from apparent stochasticity at small scales, and that unaccountable variation at local scales need not impede tests for similar patterns at broader scales. Most ecologists work at scales where complexity tends to be greatest (i.e. local) and is likely to be explained by special and unique events. It is encouraging, therefore, to observe that patterns can emerge from complexity at local scales to provide new opportunities to answer some of the more interesting questions about the relative importance of processes across the vast parts of the worlds coast.Communicated by M.S. Johnson, Crawley     

Monitoring of waste deposit derived groundwater contamination with organic tracers

Specific anthropogenic substances derived from seepage and leakage water from a waste deposit landfill were analysed in groundwater and drainage effluents using gas chromatography-mass spectrometry (GC/MS). Here, we demonstrate the application of an organic marker approach to study lateral and vertical distribution of contamination as well as the long-term emission behaviour. Source-specific and environmentally-stable pesticides, plasticisers and pharmaceuticals, such as N,N-diethyl toluamide, N-butyl benzene sulfonamide, clofibric acid, mecoprop and bisphenol A, were quantitatively analysed. A distinct lateral expansion was detected. Although temporal variations were high, no significant trend was observed.     

Neighborhood Level Spatial Analysis of the Relationship Between Alcohol Outlet Density and Criminal Violence

Misuse of alcohol is a significant public health problem, potentially resulting in unintentional injuries, motor vehicle crashes, drownings, and, perhaps of greatest concern, serious acts of violence, including assaults, rapes, suicides, and homicides. Although previous research establishes a link between alcohol consumption increased levels of violence, studies relating the density of alcohol outlets (e.g., restaurants, bars, liquor stores) and the likelihood of violent crime have been less common. In this paper we test for such a relationship at the small area level, using data from 79 neighborhoods in the city of Minneapolis, Minnesota. We adopt a fully Bayesian point of view using Markov chain Monte Carlo (MCMC) computational methods as available in the popular and freely available WinBUGS language. Our models control for important covariates (e.g., neighborhood racial heterogeneity, age heterogeneity) and also account for spatial association in unexplained variability using conditionally autoregressive (CAR) random effects. Our results indicate a significant positive relationship between alcohol outlet density and violent crime, while also permitting easy mapping of neighborhood-level predicted and residual values, the former useful for intervention in the most at-risk neighborhoods and the latter potentially useful in identifying covariates still missing from the fixed effects portion of the model.     

Egg laying and embryonic-larval development in the snail<Emphasis Type="Italic"> Thais (Stramonita) chocolata</Emphasis> (Duclos, 1832) with observations on its evolutionary relationships within the Muricidae

Oviposition and embryonic-larval development are described for the muricacean snail Thais (Stramonita) chocolata from the Southeast Pacific coast. As with numerous other muricacean snails, this species engages in communal egg laying, with females depositing egg capsules in clusters on subtidal rocks. Each cluster of capsules contains 100–150 pedunculate, ampulliform egg capsules, with each capsule containing an average of 2,600 small (130 m) eggs. Intracapsular development was followed using light and scanning electron microscopy to describe the successive embryonic stages of the species. Free-swimming veliger larvae of about 225 m length were released from capsules after 49 days incubation at 13.6°C. The planktotrophic larvae were cultured in seawater aquaria by feeding with pure cultures of phytoplankton, recording growth and form of the larvae. Larvae reached competence after 4 months at 22°C, at 1,450–1,740 m in size, and a few larvae were observed through metamorphosis and early definitive growth. The embryonic-larval development of T. chocolata coincides with the general characteristics of the ontogeny observed in other Thais species as well as of other genera of the Rapaninae such as Concholepas. This lent support to grouping these genera into a single clade. The lack of knowledge of the development of free larvae of Thais spp. means that we do not know whether these similarities also include an extensive larval phase as generally characteristic of other members of the clade. The mode of development may be useful in characterizing some clades of this family. Thus for example, the transference of some Thais to the genus Nucella (Subfamily Ocenebrinae) is supported by differences in the mode of embryonic development, which differentiates these subfamilies. Paleobiological data reported for Neogastropoda allow postulation of primitiveness in planktotrophic larval development compared to more recent developmental strategies such as direct development of different types, which characterize various clades of this family.Communicated by O. Kinne, Oldendorf/Luhe